The present invention relates to a speed-governing apparatus for an internal combustion engine, in particular, a diesel engine, for controlling the number of revolutions thereof and, more particularly, relates to a speed-governing apparatus for setting the amount of fuel to be injected by a fuel injection pump of a diesel engine, based on an electrical instruction.
In a diesel engine, a predetermined amount of metered fuel is supplied to a fuel injection valve, one of which is provided for each of a plurality of cylinders of the engine. The metered fuel is injected from each fuel injection valve into the engine.
In this case, the control function for setting the amount of fuel to be injected is carried out on the basis of an instruction corresponding to the prevailing engine conditions, for example, the number of revolutions perminute (engine RPM) the amount of intake air, and the like.
Such fuel injection quantity control is performed in accordance with a calculated result indicating an optimal amount of fuel to be injected, arrived at on the basis of detection signals supplied by engine condition-detecting means, such as an engine RPM sensor, an intake air quantity sensor, and the like, incorporated in the diesel engine. Stated more precisely, the injection quantity control member of the fuel injection pump is driven in accordance with an electrical signal corresponding to the above-mentioned calculated result. Means considered as being suitable for driving the injection quantity control member include an electromagnetic actuator mechanism, and an electrical control means in the form of a combination of the actuator mechanism and a hydraulic mechanism.
In the course of performing fuel injection quantity control, the position of the injection quantity control member corresponds to the amount of fuel to be injected. The position of the control member is detected by using an electrical type position detector, feedback control for positioning the control member being performed on the basis of this detection signal.
When fuel injection quantity control is to be executed, the relationship between the position of the control member and the amount of fuel to be injected, as well as the relative positional relationship between the control member and the position detector, must be accurately determined. However, in practice, it is difficult to assemble the engine so as to precisely set the relative positional relationship between the control member and the position detector. In addition, it is difficult to determine if the detection signal from the position detector accurately represents the actual amount of fuel to be injected.